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Sizing an Exhaust Fan

Sizing an Exhaust Fan

The following data should help you in determining the CFM capacity of a fan for a specific room. The values are easy to calculate. There are minimum standards to follow. Here is where they are put to use. Let's take a small kitchen for an example. Say the kitchen measures 10 feet by 12 feet with an eight foot ceiling. That computes to 960 cubic feet of air in the room. The minimum requirements say that this air should be changed 15 times an hour. This means that a fan must have the ability to move 14,400 cubic feet of air in an hour. Since there are 60 minutes in an hour, we must divide the 14,400 by 60 to get CFM (cubic feet per minute). Cubic feet of 14,400 per hour divided by 60 equals 240 CFM. Nothing to it! Table Values courtesy of Nutone, Inc.

The room area is listed in square feet. All values below the listed room size represent the fan's minimum capacity shown in cubic feet per minute.

Room Area in Square Feet

Fan Capacity in CFM for a KITCHEN Fan Capacity in CFM for a BATHROOM Fan Capacity in CFM for Other Rooms
35 N/A 40 N/A
45 N/A 50 N/A
55 N/A 60 45
65 N/A 70 55
75 150 80 60
85 170 90 70
95 190 100 80
100 200 110 80
125 250 140 100
150 300 160 120
175 350 N/A 140
200 400 N/A 160
225 450 N/A 180
250 500 N/A 200
310 620 N/A 250
375 750 N/A 300
435 870 N/A 350
500 1,000 N/A 400
560 1,120 N/A 450
625 1,250 N/A 500
685 1,370 N/A -

Column B98


5 Responses to Sizing an Exhaust Fan

  1. What size (CFM) remote kitchen exhaust fan should I use to properly vent a 4- burner gas cooktop? The distance from the exhaust above the stove to fan on the outside wall is 14 feet and there are 3 x 90 degree bends to get to the outer wall to vent.

    Does an induction cooktop require less CFM venting?


  2. kitchen is 8'x8' and 10 ft high.ie say 650 Ccu ft of air.air is to be changed 15 times an hour. therefore fan must move650x15 equuals to
    say10000times. on dividing by 60, we get160cfm
    pl advise will 150 cfm will be sufficent or shud igo higher cfm
    is dimension fan meaningfu like 6'/8'/10'/12' size or shape square / square/ is relevant
    Pl advise on urgent basi and oblige.
    Thank you

  3. Hi, I am working on a school project, how to design a heating and cooling for a commercial building of 60, 000 sq ft. Any commercial building will do, I am planning on design a system for a super market, I don't how to start this project, perhaps you can give me some ideas thanks.

  4. I want to design a machine , which needs exhaust fan . This machine should be placed in lawn or some open area to capture the air surrounding that machine. How will I know the capacity as amount of air is not known

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